Yes, that DM story is a load of far-fetched shite.
And what twaddle are the conspiracy theories. So Diana was considering moving abroad, marrying Dodi and taking William and Harry .... erm - William and Harry were not 4 and 2 years old at that point, they were something like 14 and 12 - their own opinion on where they wanted to live would have been valid and taken into account. And if she'd provided them with a Muslim half-brother or sister, so what? That child wouldn't have been 'royal' at all, so it would have had minimal impact on the 'establishment'.